Fuse integrity indicator



March 13, 1934. F, c, LA MAR FUSE INTEGRITY INDICATOR Filed July so, 1932 INVENTOR- BY f ATTO ZNEY- Patented Mar. 13, 1934 UNITED STATES PATENT OFFICE FUSE INTEGRITY INDICATOR Frank 0. La Mar, New York, N. Y.

Application July 30, 1932, Serial No. 626,592

This invention relates to electrical fuses, especially to electrical fuses of the cartridge type, and more particularly-to an indicator for such fuses which acts to give information as to the integrity of the fusible element.

It is well understood by those skilled in the electrical art that safety requires all circuits which carry or are capable of carrying an appreciable amount of current must have safety devices inserted in them to prevent an excessive flow of current under abnormal conditions.

A common safety device is the well known fuse made of a strip of metal which will melt upon the flow therethrough of an undesirable heavy current.

Fuses are made of many forms amongst which is the cartridge fuse which may be either of the ferrule type or the knife blade type. In the case of either type, there is no convenient and desirable means of simple form by which the fact that the fusible metal has melted may be indicated except by removing the fuse from its position and disassembling it.

' A principal object of applicants invention is the provision of a means by which the integrity of the fusible element of a fuse may be ascertained by a visual inspection without disassembling the fuse or disturbing the position thereof.

Other objects and advantages will appear as the description of the particular physical embodiment selected to illustrate the invention progresses and the novel features of the invention will be particularly pointed out in the appended claims. y

In describing the invention in detail and the particular physical embodiment selected to illustrate the invention. reference will be had to the accompanying drawing, and the several views thereof, wherein like characters of reference designate corresponding parts throughout the several views, and in which:

Figure 1 is a side elevational view of a conventional knife blade cartridge fuse in place in the usual and conventional clips with an indicator embodying applicants invention shown therewith; Fig. 2 is a cross-sectional view upon the plane indicated by the line IIII of Fig. 1, viewed in the direction of thearrows at the ends of the line; Fig. 3 is a longitudinal sectional view on the plane indicated by the line III-III of Fig. 2- viewed in the direction of the arrows at the ends of the line; Fig. 4 is a. perspective view of an indicator of applicants invention. electrical discharge type, but also the conductor Numeral 1 designates an ordinary and conven- 16 from one terminal of the lamp to the metallic 'tional mounting panel upon which are'the ordiclip 13, the conductor 17 connecting with a 2 Claims.

nary and well known binding bolts 2 and 3 for attaching the conducting wires 4 and 5 of a circuit in which a fuse is to be inserted. Bolts 2 and 3 are connected by means of metallic strips 6 and '7 to the usual fuse clips 8 and 9.

A usual and conventional form of knife blade cartridge fuse 10 is positioned connecting the clips 8 and 9.

In order to visually indicate the integrity of the thermal element of the fuse 10 applicant pro vides an indicator which embodies a lamp 11. This lamp 11, in accordance with applicants invention, is connected between the terminals of r the clips, that is, between 4 and 5. When the fuse 10 is intact the lamp exhibits no glow but when the thermal element of the fuse 10 has been destroyed, the lamp 11 becomes illuminated.

Various forms of fuse integrity indicators have been devised by applicant and others which are attached and mounted upon the fuse 10. For some reasons this form of fuse indicator is disadvantageous in that if a fuse element becomes destroyed it is necessary not only to remove the fuse, as 10, but also to remove the fuse indicator. This requires the handling and manipulation of two parts. Ease of manipulation would be facilitated by obviating the necessity of handling both the fuse and the fuse indicator upon the destruction of the thermal element of the fuse.

Applicants form of fuse indicator includes a protecting tube 12 formed at each end with a clip. At one end a right angle or bent over clip 13 is attached to the tube. At the other end a substantial straight clip 14 is attached to the tube. The straight clip 14, however, has a bent up portion 15 formed intermediate its ends.

The form of clips proposed by applicant enables the tube 12 to be attached to the fuse clips 8 and 9, as shown in Figs. 1 and 2, that is, the clip 13 is hooked over the upper fuse clip and the lowerclip 14 is pushed inwardly so that the protuberance 15 extends upwardly beyond the inside edge of the lower fuse clip 8. This form of mounting not only securely positions the tube 12 and the lamp 11 carried thereby, but it also provides a good electrical contact with the metal of the fuse clips, and in addition positions the indicator independently of the fuse l0 and out of the way of the fuse 10, so that the fuse 10 may be removed without in any way disturbing the indicator.

The tube 12 not only contains theindicating lamp 11, which is preferably of the low potential resistance 18, preferably of the grid leak type, and the conductor 19 connecting with the metallic clip 14. 4

Applicant prefers to provide an opening 20 in the tube 12 by which the condition of the lamp 11 may be observed. This opening is preferably so formed inthe tube that the condition of the lamp may be observed not only from a position directly in front of the fuse 10 but also in a position somewhat to the side.

The improved indicator of applicants invention is not only inexpensive to manufacture, but is extremely simple to install, and while perfectly serving its purpose is entirely out of a position where it will in any wise interfere with the ordinary and well known manipulation of the cartridge fuse.

Although I have described one particular physical embodiment of my invention, and the principle and construction thereof, nevertheless, I desire to have it understood that the particular form selected is merely illustrative but does not exhaust the possible physical embodiments of the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric thermal fuse integrity indicator, in combination: a lamp provided'with terminals; means to protect and support the lamp; and

means adapted to attach and maintain the said support in a position adjacent two aligned knife blade fuse clips, said means including a hook like metallic element at one end of the body for attaching that end to a clip, and a metallic resilient snap like connector at the other end of the body for connecting that end of the body with another fuse clip; and means for connecting the terminals of the lamp with the said fuse clips.

2. A fuse integrity indicator for connection between two clips holding the knife blades of a knife blade thermal fuse, in combination: an elongated hollow body; a metallic substantially right angle clip attached to one end of the hollow body; a substantially straight clip formed with a projection intermediate its ends attached to the other end of the hollow body; a lamp having terminals within and supported by the hollow body; means electrically connecting the terminals of the lamp to the clips, said means including an interposed resistance whereby the right angle clip may be hooked over an upper fuse clip and whereby the projection of the substantially straight clip may be positioned on the opposite side of a lower fuse clip from that upon which the tube rests so that the lamp may serve as an indicator for the integrity of the fusible element of the fuse.

FRANK C. LA MAR. 

